In general, the present invention relates to the evaluation of materials that have dynamic thermal-, moisture-, and/or energy-storage properties, such as materials containing a xe2x80x98phase changexe2x80x99 component (whether it is as microspheres filled with phase change material, microcapsules containing phase change material, as phase change material incorporated into the structure of the fibers, as hollow fibers or pores filled with phase change material, phase change material impregnated upon non-hollow fibers, as a laminate or coating with a phase change layer, etc.) and other materials used in moisture and/or thermal management systems for apparel, bedding, drapery, upholstery, flooring/carpets, ceilings, wall-coverings, walls (including interior and supporting walls of ground vehicles, aircraft, watercrafts, etc.), wood planks, drywall, and so on. More particularly, the invention relates to a new evaluation apparatus, method for evaluating materials, including thermally-dynamic materials, and an associated novel metric (herein referred to as a temperature regulating factor, TRF) for comparing thermal-regulating ability of such materials that more-readily simulates the dynamic, or transient, nature of associated xe2x80x98realxe2x80x99 environments in which these materials are used (whether the simulated environment is comprised of a transient response that is generally random, periodic, or some combination thereof).
The development of xe2x80x98smartxe2x80x99 materials to better thermally regulate an environment (be it the microclimate of human, his/her pet, or farm animal in proximity to cloth, the interior of a vehicle or aircraft, inside of living/office spaces, research laboratories, and production facilities, and so on) has far outpaced the conventional methods used to evaluate such materials to the point of making conventional testing methods and the associated quantities used for comparison, nearly obsolete. High performance materials continue to be evaluated using known techniques whereby the material is exposed to a static environmentxe2x80x94test results focus simply on insulation.
For example, in the textile arena, the conventional method for measuring thermal properties of textiles is described in the American Society for Testing and Materials"" (ASTM) Standard D 1518 entitled, xe2x80x9cStandard Test Method for Thermal Transmittance of Textile Materials.xe2x80x9d This standard is currently employed to determine the overall thermal transmittance coefficients due to the combined action of conduction, convection, and radiation for dry textile specimens. The test apparatus consists of a xe2x80x98guardedxe2x80x99 hot plate assembly enclosed in an environmental chamber. Fabric is wrapped around the guarded hot plate, which is intended to simulate human skin. The top hot plate, its xe2x80x98guardxe2x80x99 (a second hot plate) and fabric are placed in an environmental enclosure, which is maintained at a cooler temperature than the guarded hot plate, between 4.5 and 21.1xc2x0 C. (40-70xc2x0 F.). The hot plate is maintained between 33.3 and 35xc2x0 C. (92-95xc2x0 F.). The guard is necessary to ensure that thermal energy is transferred out of the guarded hot plate assembly through the fabric side, only. This test procedure was designed to create a temperature gradient through the fabric, allowing one to measure a value for rate of heat transfer from the hot plate to the opposite, or outwardly directed, side of the fabric. This rate of heat transfer has been used to characterize the insulative capability of the fabric sample. As one can appreciate, this complicated ASTM D 1518 test simply cannot appropriately characterize thermally-dynamic materials used and/or under development.
The ASTM textile test apparatus and protocol have some known disadvantages (which give inconsistent results): The fabric oftentimes makes poor contact with the guarded hot plate; the convection coefficient over the fabric may vary if appropriate measures of control are not employed which affects results; and especially since the protocol requires close control of several of the variable test parameters, reliability and accuracy of results obtained using ASTM D 1518 have been shown by researchers to vary. Furthermore, since research and product analysis has focused on measures of insulation, ASTM D 1518 is strictly limited to simple insulation measurements, it does not simulate real environmental conditions, and cannot adequately measure the enhanced thermal regulation performance obtained by adding phase change materials to a textile. Other than the ASTM D 1518 method, no other U.S. standard method for evaluating the thermal regulating ability/properties of textiles, let alone thermally-dynamic materials, is known by applicants.
Therefore, a new useful apparatus, method and associated metric is needed for the comparative evaluation of materials, whether the materials have a dynamic thermal-, moisture-, and/or energy-storage component designed for expected use in a xe2x80x98transientxe2x80x99 environment. Without reasonable, accurate, and cost-effective solutions at hand for evaluating materials in a timely, reproducible manner, it has been very difficult to make useful comparison-evaluations of products fabricated using the materials. Unlike the conventional systems currently in use, the innovative apparatus, and associated method and metric for characterizing the thermal (or energy) regulating ability of the material under evaluation (be it a flexible textile/fabric, carpet, wall laminate, fiberglass, wood product, and so on) more-accurately simulates the conditions under which such dynamic materials are usedxe2x80x94giving much more accurate results than methods/instruments currently-available. In the spirit of design goals contemplated hereby, many different types of materials, including those with a dynamic thermal-, moisture-, and/or energy-storage component can be evaluated utilizing the instant invention, as will be appreciated.
It is a primary object of this invention to provide an apparatus for evaluation of a material having a first and second contact-surface, and associated method and metric for comparative characterization of the thermal-, moisture-, energy-regulating ability of a material under evaluation. Such an apparatus and method include a computer-controlled thermally-variable central element having a first and second outer surface, at least one of which may have a temperature sensor thereon, located between a first and second thermally-variable side element whereby the material can be positioned between the central element and each of these thermally-variable side elements. A multitude of materials, whether containing a dynamic moisture-, thermal-, and/or other type of energy-storage component, can be evaluated using the innovative apparatus and method.
The advantages of providing the new apparatus, method, and metric, and the very distinguishing features thereof, as described and supported can be readily appreciated.
(a) The invention affords a means by which the thermal-regulating ability of materials can be evaluated for comparative analysis, regardless of the type of material, its size/thickness, final shape, or end-use, the results of the evaluation can be used to provide information that can be compared with other materials.
(b) The apparatus and method more-readily simulates the dynamic, or transient, nature of associated xe2x80x98actualxe2x80x99 environments in which a material under evaluation are used (whether the simulated environment is comprised of a transient response that is generally random, periodic, or some combination thereof).
(c) The apparatus and method of the invention may be used to evaluate a multitude of materials of a wide variety of sheet stock/material, such as fabrics (including any flexible material made of an individual component or combination of cloth, fibers, polymeric film, sheeting, or foam, metallic foil or coating, ceramic/glass substrate, etc.xe2x80x94whether laminated or coatedxe2x80x94used in carpets, apparel, bedding, drapery, upholstery, and so on), drywall and other wall laminates, wood products and other sheet stock made of a cellulous material, fiberglass, and so on. Once the pressure regulator has been calibrated to apply the preselected pressure to the surface of a material, one apparatus may accommodate many different material samples (as a single sheet or two separately-hung sheets).
(d) The apparatus and method of the invention provide comparative results in a cost-effective manner without requiring that conditions surrounding the apparatus be so closely regulated/controlled, yet automatically control values measured and tracked, such as the magnitude and preselected variability of thermal energy/flux into the central element, surface temperature of both outer surfaces of the central as well as the exterior surfaces of both side elements, and duration of evaluation, using currently available computer processing and data acquisition equipment.
Briefly described, once again, the invention includes an apparatus and method for evaluation of a material having a first and second contact-surface. The apparatus includes a computer-controlled thermally-variable central element comprising a first and second outer surface, at least one outer surface having at least one temperature sensor thereon. Facing the first outer surface is a first exterior surface of a first thermally-variable side element, and facing the second outer surface is a second exterior surface of a second thermally-variable side element. A mechanism is included that operates to move at least the first exterior surface toward the thermally-variable central element to apply a generally uniform pressure against the material contact-surfaces once the material has been positioned. A particular material is preferably positioned for evaluation (whether as a single large piece, or as two individual pieces) between the central element""s first outer surface and the first exterior surface, and between the central element""s second outer surface and the second exterior surface. A computer processor in communication with a computer memory can be used for controlling the central and side elements. As defined for reference purposes, the first and second outer surfaces have a respective measured temperature value of THigh-1 and THigh-2, and the first and second exterior surfaces have a respective selected temperature value of TLow-1 and TLow-2.
Additional further distinguishing features include: A first heat sink in proximity to a backside of the first side element, a second heat sink in proximity to a backside of the second side element, and a linear bearing upon which the central element, the first and second side elements, and the respective heat sinks are mounted. The thermally-variable central element can comprise a relatively flexible plate-like structure oriented generally vertically. The thermally-variable side elements can comprise a metal alloy plate-like structure, whereby respective first and second exterior surfaces are contoured to mate with respective first and second outer surfaces of the central element, when in contact. The mechanism for moving can comprise a surface-contact pressure regulator and a lever for moving the first heat sink and first side element along the linear bearing. A first thermoelectric cooler can be sandwiched between the first side element and the first heat sink, and a second thermoelectric cooler can be sandwiched between the second side element and a second heat sink.
The method characterized comprising the steps of: positioning the material between a first outer surface, at a temperature THigh-1, of a computer-controlled thermally-variable central element and a first exterior surface of a first thermally-variable side element, and between a second outer surface, at a temperature THigh-2, of the central element and a second exterior surface of a second thermally-variable side element; moving at least one side element toward the central element to apply a generally uniform pressure against the material contact-surfaces; and measuring a temperature value of the first and second exterior surfaces, respectively TLow-1 and TLow-2, whereby THigh-1 and THigh-1 are maintained higher than values TLow-1 and TLow-2. One can control TLow-1 and TLow-2, through feedback carried out using a computer processor. The energy input into the central element can be according to a preselected transient response comprising a maximum and a minimum thermal flux value, qmax and qmin.
Further distinguishing steps include: automatically transferring and controlling an energy input into the central element, and automatically measuring values THigh-1 and THigh-1 using the computer processor; automatically calculating an xe2x80x9cRxe2x80x9d value for the material by finding a difference (xcex94TSSmean) between a mean steady state value, TSSmean-High, of THigh-1 and THigh-2 and a mean steady state value, TSSmean-High, of TLow-1 and TLow-2, and dividing this difference (xcex94TSSmean) by a steady state thermal flux value, qSSinput, representing an energy input; drawing thermal energy outwardly from each of the exterior surfaces of respective side elements; automatically determining at least a mean maximum value, Tmean-Highmax, of THigh-1 and THigh-2 for the maximum temperatures reached during the preselected transient response and a mean min. value, Tmean-Highmin, of THigh-1 and THigh-2 for the minimum temperatures reached during the preselected transient response; automatically calculating a thermal metric (TRF) according to the following expression (which yields a dimensionless result):   TRF  =                    (                              T                          mean              -                              High                ⁢                                  xe2x80x83                                ⁢                max                                              -                      T                          mean              -                              High                ⁢                                  xe2x80x83                                ⁢                min                                                    )                    (                              q            max                    -                      q            min                          )              *                  1        R            .      
The preselected transient response can be set to generally simulate the thermal fluctuations in a mammalian body during periods of rest and activity. Calculated TRF and R values can be readily displayed for communication to a user (e.g., by way of display screen) or stored and further transferred to on-site or off-site, remote, data acquisition equipment.